At the exact halfway point of the NBA season, the Boston Celtics are exactly where they were a year ago, fighting with a bunch of teams in the middle of the pack in the Eastern Conference and trying to hold on to one of the final playoff spots. The difference is their level of play - the Celtics' point differential has improved from +0.2 to +3.2 and their win percentage has jumped from .488 to .524. They have gotten better just to stay in place, as the East is far more competitive than it was last season. Boston is 3.5 games back of the No. 2 seed and 2.5 games ahead of the No. 12 seed.

It’s a far cry from the preseason expectations surrounding the team, where there was talk of the Celtics being this year’s version of the Atlanta Hawks. Many had them pegged as the second best team in the East and there were a number of statistical models that had them flirting with 50 wins. There’s still time for them to make a push to the top of the standings, but they don’t have much of a margin for error when it comes to staying in the playoff race either.

The biggest difference between them and the Hawks is they weren’t adding a player anywhere near the caliber of Al Horford, whose return from a season-ending injury the year before is what spurred Atlanta’s jump from a No. 8 seed to a No. 1 seed. Horford is one of the most complete big men in the league, a do everything 6’10+ player who can defend either frontcourt position, create a shot off the dribble or in the post, stretch the floor out to the three-point line and facilitate offense for his teammates. While he may not have the high scoring totals of a prototypical star, he can be the lynchpin of a high-level team on both sides of the ball.

It’s the same story with Paul Millsap, who made his first All-Star team of his career last season. Millsap has gotten better in each season in the league and he’s one of the biggest beneficiaries of the increasing push to small-ball. When he first came into the NBA in the middle of the 2000’s, he was moved from PF to SF because there were concerns he wouldn’t be able to match up with some of the bigger players at his position at 6’7. These days, he can be incredibly effective as a small-ball C. Millsap and Horford are one of the best big men tandems in the league and they give the Hawks a tremendous amount of versatility - they can hang with big front-lines and exploit small ones.

The Celtics, on the other hand, have a bunch of mismatched parts upfront. They began the season with Tyler Zeller and David Lee starting and neither player is even in the rotation three months later. Zeller is a thoroughly average 7’0 on both sides of the ball who doesn’t have a lot of defined strengths as a player while Lee has wound up at the end of the bench in each of the last two teams he has been on. He’s like the exact opposite of Horford - he can post gaudy scoring totals but he can’t defend a position or protect the rim or stretch the floor.

Brad Stevens has gone mainly with the trio of Amir Johnson, Jared Sullinger and Kelly Olynyk, each of whom have flaws of their own. Johnson is the most complete big man but he’s not capable of creating his own offense. Sullinger can score in the post and clean the boards at a high level but he’s undersized for a center and not quick enough to defend on the perimeter. Olynyk is the best shooter and all-around offensive player but he’s a defensive disaster who doesn’t have Johnson’s quickness or Sullinger’s strength.

Where Boston has found the most success is going small, sliding Jonas Jerebko and Jae Crowder down a position to PF and playing pure four-out basketball. Crowder has by far the best net rating on the team (+9.0) and he’s a mainstay on most of their most productive line-ups. When he’s playing as a PF, they spread the floor on offense and can switch pick-and-rolls on defense and there’s more room in their line-up to mix and match with their assortment of perimeter players. The strength of their team is on the perimeter and they are at their best when they can speed up the tempo of the game, pressure the opposing team and score going defense to offense.

The problem is that even playing 4-out basketball still requires a big man who can anchor the team on both sides of the ball. They can play Olynyk at the 5 and spread the floor wide open but that leaves a glaring hole at the front of the rim. They can play Johnson at the 5 and add more of a defensive presence but that means there isn’t a lot of shot-creating in the frontcourt. Sullinger is better on offense than Johnson and better on defense than Olynyk but playing him at the 5 means less floor spacing than Olynyk provides and less defense than Johnson. Stevens is constantly balancing one side of the floor off the other with his rotations upfront and the result is a team that hasn’t been able to maintain much consistency this season.

There’s no easy answer for the Celtics in terms of upgrading their roster because even in the modern NBA two-way big men are still worth their weight in the gold. They have a lot of trade assets piled up but it still takes two teams to tango while Boston hasn’t been known as much of a free-agent destination over the years. There’s more high-upside young talent on the teams around them in the standings - the Detroit Pistons, Indiana Pacers, New York Knicks and Washington Wizards - and they might have been stuck on the dreaded “mediocity treadmill” and running the Red Queen’s Race for years were it not for the lifeline generously provided to them by the Brooklyn Nets.

Boston has Brooklyn’s unprotected picks in 2016 and 2018 and the right to swap picks in 2017 and there’s a good chance that all of those picks end up in the Top 7, if not the Top 5. They will have multiple cracks at drafting a future superstar upfront and they will have the benefit of not having to rush their young players into leading roles before they are ready. They are in a pretty similar position to where the Utah Jazz were a few years ago, when they were competing for a playoff spot while simultaneously building a young core for the future.

However, as the Jazz have found out, it takes a long time for a team whose best players are under 25 to put everything together. Big men take forever to develop, especially in an era where the best ones declare for the draft at the age of 19, and guys the Celtics draft in 2016 might not be ready to play big roles on a contender until the 2020’s. Boston will be tempted to pull a trigger on another trade and accelerate their timetable to rebuild, but there’s no guarantee that they find the right trade partner who wants to unload a franchise-caliber big man for a bunch of picks that won’t pay off for a long time.

The obvious candidate to make a move is the Sacramento Kings and acquiring an elite two-way big man like DeMarcus Cousins while he’s locked into an affordable long-term contract could change the trajectory of the Celtics franchise. The other intriguing option would be Kevin Love, who looks likely to be the fall guy in Cleveland if things don’t work out this season. Love would give them an elite offensive player upfront but it would require moving a lot of things around in order to build a team around him that maximizes his strengths and minimizes his weaknesses.

The good news for the Celtics is they have the pieces to be very flexible - they have a lot of young players signed to affordable contracts, a ton of future draft picks and no bad contracts weighing their cap sheet down. The bad news is they are trying to make the jump from good to great - the hardest leap to make in the NBA - without any of the pieces on the roster necessary to make that possible. You can’t follow the Hawks' blueprint without having the Hawks' big men.